Patent EA-003236-B1 (EA)
Title: Method of scanning a recorded disc for defects and recording device for recording information on a disc-shaped recording medium
Inventor: VAN DEN ENDEN GIJSBERT J
IPC: G11B20/12
Filed: 2000-07-12
Abstract: 1. A method of examining a recording track (2) of a record carrier (1) for the presence of a defect, wherein the track to be examined is followed and the resulting tracking signal is monitored, and wherein the examined recording track is rated on the basis of characteristics of the resulting tracking signal. 2. A method as claimed in Claim 1, wherein the examined recording track is rated as being defective if the absolute value of the tracking signal has a value which exceeds a predetermined signal threshold for a predetermined period of time or longer. 3. A method as claimed in Claim 2, wherein the tracking signal has a nominal signal value of zero which corresponds to the center of a track, and has a maximum value which corresponds to a maximum lateral deviation with respect to the center of a track, and wherein a level of a preselected fraction of said maximum value is chosen as signal threshold, which preselected fraction is preferably equal to approximately 0.5. 4. A method as claimed in Claim 2 or 3, wherein said predetermined period of time lies in a range from approximately 50 mus to approximately 75 mus, and is preferably approximately 60 mus. 5. A method of examining a record carrier (1) for the presence of spot defects (12; 13), the method comprising the following steps: a) examining the integrity of predetermined test tracks (2T) of the record carrier (1), preferably by means of a method as claimed in any one of the preceding Claims; b) examining the integrity of tracks (2) adjacent the relevant test track (2T2; 2T3) each time that upon the examination a test track (2T2; 2T3) appears to be defective, in order to determine in this way the number (X) of tracks (2) affected by the same spot defect (12; 13); c) entering the relevant tracks (2) in a defect list each time that the number (X) thus determined in the step (b) is greater than a predetermined threshold value (M); d) storing the defect list in a memory (25). 6. A method as claimed in Claim 5, wherein each time a predetermined number (N) of tracks (2) between successive test tracks (2T) is skipped, said number (N) being preferably equal to approximately 50. 7. A method as claimed in Claim 5 or 6, wherein the defect list is recorded on the examined record carrier (1). 8. A method of recording information, particularly real time video, on a record carrier (1) of the type having a multitude of concentric substantially circular recording tracks (2), particularly a DVR disc, the method comprising the steps of: -first providing, in an examination phase, a defect list of tracks affected by a comparatively large spot defect (13) by means of a method as claimed in any one of the Claims 5-7; -subsequently recording information on the disc in a recording phase while reference is made to said defect list, the recording tracks included in said defect list being skipped in the recording process. 9. A method of examining a record carrier (1) for the presence of spot defects (12; 13), comprising the following steps: a) examining the integrity of predetermined test tracks (2T) of the record carrier (1), preferably by means of a method as claimed in any one of the Claims 1-4; b) entering the relevant tracks (2T2; 2T3) in a primary defect list each time that upon the examination of a test track (2T2; 2T3) it appears to be defective, and, optionally, entering tracks (2) situated in a suspect area (3T2; 3T3) at opposite sides of the relevant test track (2T2; 2T3) in an alarm list; c) storing the primary defect list and, if applicable, the alarm list in a memory (25). 10. A method as claimed in claim 9, wherein the step b) further comprises entering tracks (2) situated in a suspect area (3T2; 3T3) at opposite sides of the relevant test tracks (2T2; 2T3) in an alarm list of tracks (2), and the step c) further comprises an operation of storing the alarm list of tracks in the memory. 11. A method as claimed in Claim 10, wherein each time a predetermined number (N) of tracks (2) between successive test tracks (2T) is skipped, and wherein each suspect area always extends from the relevant test track (2T2; 2T3) to the directly preceding and the directly following test track, respectively, said number (N) being preferably approximately 50. 12. A method of recording information, particularly real time video, on a record carrier (1) of the type having a multitude of concentric substantially circular recording tracks (2), particularly a DVR disc, the method comprising the steps of -first providing, in a primary examination phase, a primary defect list of test tracks (2T2; 2T3) having a defect and, optionally, an alarm list of tracks (2) situated in a suspect area (3T2; 3T3) at opposite sides of the relevant test tracks (2T2; 2T3), by means of a method as claimed in any one of the Claims 9-11; -subsequently recording information on the disc in a recording phase while reference is made to said primary defect list and said optional alarm list, the recording tracks included in said primary defect list as well as the tracks (2) situated in a suspect area (3T2; 3T3) at opposite sides of the relevant test tracks (2T2; 2T3) being skipped in the recording process; -subsequently examining the integrity of the tracks (2) in said suspect areas (3T2; 3T3) in a secondary examination phase, in order to determine in this way the number (X) of tracks (2) affected by the same spot defect (12; 13); -entering the relevant tracks (2) in a secondary defect list each time that the number (X) thus determined is greater than a predetermined threshold value (M). 13. A method as claimed in Claim 12, wherein the secondary defect list is recorded on the examined record carrier (1). 14. A method of recording information in a recording track (2) of a record carrier (1), wherein the resulting tracking signal is monitored, wherein the tracking signal has a nominal signal value of zero which corresponds to the center of a track, and has a maximum value which corresponds to a maximum lateral deviation with respect to the center of a track, wherein the recording process is discontinued if the absolute value of the tracking signal for a predetermined period of time exceeds a preselected fraction of said maximum value, which preselected fraction is preferably equal to approximately 2/3. 15. A method as claimed in Claim 14, wherein said predetermined period of time lies in a range from approximately 50 mus to approximately 75 mus. 16. A recording device (20) suitable for the recording of information, particularly real time video or audio, on a record carrier (1) of the type comprising a multitude of concentric substantially circular recording tracks (2), particularly an optical disc, which recording device comprises: -a control unit (22); -a write/read unit (21) adapted to aim a laser beam at a track (2) of a record carrier (1) under control of the control unit (22) and to receive laser light reflected from the disc (1), and further adapted to supply a tracking signal to the control unit (22), which tracking signal has been determined on the basis of the reflected laser light; wherein the control unit (22) is adapted to carry out the method as claimed in any one of the Claims 1-15.